main(){
  //数值类型
  num age=18;
  print(age);
  age=19.5;

  int age2=18;
  print(age2);
  age2=19;
  print(age2);

  double age3=18.5;
  print(age3);
  age3=19.5;
  print(age3);

  //字符串类型
  String name='张三';
  print(name);
  name='李四';
  print(name);
  name='王五';
  print(name);

  String str='hello'+'world';
  print(str);

  //布尔类型
  bool isVip=true;
  print(isVip);
  isVip=false;
  print(isVip);


}